Add support for resource metrics (#18057)

Add a new endpoint for "resource" metrics `/v2/metrics/resource`

This should return system metrics related to drives, network, CPU and
memory. Except for drives, other metrics should have corresponding "avg"
and "max" values also.

Reuse the real-time feature to capture the required data,
introducing CPU and memory metrics in it.

Collect the data every minute and keep updating the average and max values
accordingly, returning the latest values when the API is called.

cmd/metrics-realtime.go

@@ -19,12 +19,15 @@ package cmd
 
 import (
 	"context"
+	"fmt"
 	"net/http"
 	"time"
 
 	"github.com/minio/madmin-go/v3"
 	"github.com/minio/minio/internal/disk"
 	"github.com/minio/minio/internal/net"
+	c "github.com/shirou/gopsutil/v3/cpu"
+	"github.com/shirou/gopsutil/v3/load"
 )
 
 type collectMetricsOpts struct {
@@ -89,6 +92,34 @@ func collectLocalMetrics(types madmin.MetricType, opts collectMetricsOpts) (m ma
 			m.Aggregated.Net.NetStats = netStats
 		}
 	}
+	if types.Contains(madmin.MetricsMem) {
+		m.Aggregated.Mem = &madmin.MemMetrics{
+			CollectedAt: UTCNow(),
+		}
+		m.Aggregated.Mem.Info = madmin.GetMemInfo(GlobalContext, globalMinioAddr)
+	}
+	if types.Contains(madmin.MetricsCPU) {
+		m.Aggregated.CPU = &madmin.CPUMetrics{
+			CollectedAt: UTCNow(),
+		}
+		cm, err := c.Times(false)
+		if err != nil {
+			m.Errors = append(m.Errors, err.Error())
+		} else {
+			// not collecting per-cpu stats, so there will be only one element
+			if len(cm) == 1 {
+				m.Aggregated.CPU.TimesStat = &cm[0]
+			} else {
+				m.Errors = append(m.Errors, fmt.Sprintf("Expected one CPU stat, got %d", len(cm)))
+			}
+		}
+		loadStat, err := load.Avg()
+		if err != nil {
+			m.Errors = append(m.Errors, err.Error())
+		} else {
+			m.Aggregated.CPU.LoadStat = loadStat
+		}
+	}
 	// Add types...
 
 	// ByHost is a shallow reference, so careful about sharing.